The invention relates to a method and apparatus for cleaning a chamber.
Chemical vapor deposition (CVD) processes, such as organometallic chemical vapor deposition (OMCVD or MOCVD) processes, are commonly employed in the semiconductor, optical, and optoelectronic industries for doping or coating a substrate. Certain chemical vapor deposition processes, particularly those associated with large scale fabrication of epitaxial semiconductor devices, produce highly toxic effluent gases, such as dichlorosilane, trichlorosilane, phosphine, arsine, and hydrogen and nitrogen derivatives which have been generated in the fabrication reactor. These toxic gaseous effluents frequently contain particulate or particle-forming components, e.g., silica particles, which must be removed before the gases can be further processed, diluted mid/or neutralized, prior to ultimate discharge into the ambient environment.
Particulate-containing gaseous effluent is typically introduced into a scrubbing chamber through an inlet. The particulate matter is sticky in character and tends to adhere to the inner surface of the chamber. Various reaction chamber cleaning mechanisms (RCCMs) have been devised to prevent, or at least slow down, the buildup of particulate matter on the inner surfaces of the scrubbing chambers.
In currently available cleaning chambers, a spray jet is commonly employed to spray inside the bottom of the reaction chamber. This spray serves the dual purposes of quenching the hot gas flow and performing a water scrubbing function. A major drawback of such scrubbers is that the water spray can cause corrosion and buildup. There is a need in the art for an RCCM which provides an effective scrubbing mechanism without depending on water spray inside the reaction chamber for cooling. Such an RCCM would avoid the corrosion and buildup problems associated with presently available cleaning chambers.
RCCMs commonly use blade assemblies to scrape particulate matter from the interior surfaces of cleaning chambers. The RCCM blade assemblies of currently available RCCMs often lack sufficient strength to cut through the deposits formed on the reaction chamber wall. Such blade assemblies commonly become bent and/or twisted and thereafter permit buildup to form on the walls of the reaction chamber. There is a need in the art for an RCCM that overcomes these deficiencies in prior art blade assemblies.
Currently available RCCMs employ a push rod assembly drive mechanism to rotate the blade assembly about the inner surface of the cleaning chamber. These push rod assemblies are often not reliable, resulting in a low average service life for the cleaning chamber apparatus. The inventor has discovered that such push rod assemblies fail because the return spring becomes fatigued and fails to bend the push rod enough to engage it with the RCCM gear. The alignment key in the RCCM housing fails and causes the push rod assembly to rotate, thereby forcing the push rod to work at an angle that causes failure of the pivot pin. The alignment key and push rod assembly engagement surfaces are often damaged. The tip of the push rod assembly deforms permanently due to compressive stresses. The fasteners that attach the blade assembly to the drive mechanism often corrode and fail depending on exposure to corrosive gases. The bearings cold flow and loosen up over time, allowing water to leak into the housing. The RCCMs have no means of adjusting for manufacturing tolerance build up. Occasionally, the Teflon bearings are too tight, preventing the RCCM gear from turning. There is no indicator to monitor the functioning of the RCCM.
There is therefore a need in the art for an RCCM apparatus which overcomes all of these difficulties.
The present invention provides a reaction chamber cleaning apparatus comprising a chamber comprising a chamber wall comprising an interior surface; a blade apparatus comprising (i) at least cute annular mounting member and (ii) at least three scraping blades attached peripherally about the annular mounting member and arranged in a parallel relationship to a longitudinal axis of the chamber; and a reciprocal movement unit for rotating said scraping blade(s) circumferentially back and forth along the interior surface of said chamber to scrape the interior surface of said chamber, wherein such reciprocable movement unit comprises a reciprocable member pivotally connected to an extension member, and the extension member is pivotally connected at a peripheral position to the blade apparatus.
The present invention also provides a vortex unit comprising: (i) a top plate comprising a top surface, a bottom surface and a central opening; (ii) a generally conical outer shell attached to and extending downwardly from the top plate, in which the outer shell comprises an inner surface and a central opening that is generally aligned with the central opening of the top plate; (iii) a liquid inlet arranged in relation to the outer shell to tangentially introduce liquid into the outer shell, thereby forming a laminar sheet of fluid on the inner surface of the outer shell; (iv) a baffle attached to the lower surface of the top plate and extending generally vertically downwardly therefrom, in which the baffle comprises an inner surface, an outer surface, a bottom edge, and a central opening generally concentrically aligned with the central opening of the outer shell; (v) a concentric chamber bounded by the outer surface of the baffle, the inner surface of the outer shell, and the bottom surface of the top plate; and (vi) a concentric opening formed between the bottom edge of the baffle and the inner surface of the outer shell.
The reaction chamber cleaning apparatus and the vortex unit are suitably combined into a unitary assembly as a single article of manufacture.
In one aspect, the baffle of the vortex unit is arranged to provide a flow restriction so that during operation of the self-cleaning chamber mechanism, the concentric chamber is completely filled with liquid. The water vortex unit may also comprise a flange that accommodates attachment of the reaction chamber cleaning apparatus.
In one aspect, the liquid inlet is in fluid connection with a source of water.
In another aspect, the reaction chamber cleaning apparatus also comprises an exhaust moisture control system arranged to pass day air through the chamber to a secondary scrubbing tower.
The reaction chamber cleaning apparatus may be incorporated into an effluent abatement system by positioning the apparatus in downstream fluid flow communication with an effluent source such as a chemical vapor deposition apparatus or a semiconductor manufacturing apparatus.
In one aspect of the present invention, the blades of the reactor chamber cleaning apparatus are double-edged. Moreover, the blades preferably have a width and the reciprocating member has a range of movement, which width and range of movement are selected to provide each blade with a rotational path which overlaps with the rotational path of another blade. The blades are preferably from about 0.65 to about 0.75 inches wide, more preferably about 0.70 inches wide, and the rotation range is about 90xc2x0.
In another aspect, the reciprocable member of the reactor chamber cleaning apparatus is a piston of an air cylinder. The air cylinder is preferably equipped with a mechanism for indicating whether the cylinder is sufficiently extending and/or retracting to ensure that the apparatus is properly cleaning the chamber. For example, the mechanism may comprise one or more appropriately positioned magnetic reed switches. The mechanism for indicating whether the cylinder is sufficiently extending and retracting is preferably configured to provide an output, such as an electronic signal, indicative of whether the cylinder is sufficiently extending and/or retracting. The electronic signal may be transmitted to a CPU for further processing and/or may trigger an alarm, such as an audible alarm to indicate that the cylinder is not sufficiently extending and/or retracting.
The present invention also provides a method for using the apparatus of the invention for abating an effluent. The method generally comprises the steps of flowing liquid into the inlet so as to fill the concentric chamber with liquid and form a laminar sheet of liquid on the inner surface of the outer shell and flowing effluent into the chamber for abatement.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.